Process of producing alumina.



STES

EDWARD KENDALL, OF ELIZABETH, NEW JERSEY, ASSIG-NOR OF ONE-THIRD TO E.N. DIGKERSON, OF STOVALL, NORTH CAROLINA.

PROCESS OF PRODUCING ALUMINA.

No Drawing.

Specification of Letters Patent.

Patented Dec. 26, 1911.

Application filed January 11, 1908. Serial'No. 410,450.

To all whom it may concern:

Be it known that 1, EDWARD D. KENDALL, a citizen of the United States,residing at Elizabeth, in-the county of Union, State of New Jersey, haveinvented a new and useful Improvement in Processes of Producing Alumina,(Aluminium Oxid, A1 0 of which the following is a specification.

My invention relates to methods of separating alumina from associatedbodies in argillaceous earths, clays and shalesand the objects of thesame are to utilize cheap and abundant sources of alumina, particularlykaolinites or clays, and to provide a cheap and economical process ofobtaining water and render the clay more permeable by liquid. The claysthat are available for i this process may be residual on sedimentaryclays and may have different physical and mineralogical features, butthe essential chemical character must be that they consist chiefly ofsilicate of alumina the shales suitable for this process are not theexceedingly indurated clays (shales) but such as belng ground with waterbecome soft and more or less plasticv and like the natural hydratedaluminium silicate. The clayis to be finely pulverized and thentransferred to one of the known forms of digesters made of iron or.steel and preferably of cylindrical form and capable of bearingconsiderable pressure from within,'which digester is to be fitted withany of the suit-able and lmown appliances'for stirring the contentsthereof; into this-digester is also put aqueous solu-' tion of causticalkali. I prefer to use causticsoda (sodium hydroxid, NaOH) because 1tis efficient and cheap; the required quantity of caustic soda solution.may be supplied to the interior of the digester at the same tune andproportionately with the powdered clay, or the entire required volume ofthat solution may be led into the digester before the introduction ofthe clay. A

quantity of caustic soda solution should be used sufficient to form withthe clay, after.

agitation, a thin mud. The agitation or stirring should becontinuedunremittingly while regulated heat is applied to the digester, thedegree of which heat is limited only by the strength of the material ofthe digester and its power to safely withstand the vapor pressure fromwithin; temperatures from 1359 C. to 150 will suifice and thesametemperatures will answer in the succeeding step of the process, viz:the

treatment'with cream of lime next to be described. The time during whichthe clay shall be: so digested with the caustic soda solution varieswith the dilferent' kinds of clay and with the degree of heat maintainedand is to be determined by experimental tests; it may be three hours ormore. At the expiration of the suitable period the source of heat'is tobe removed and when the digester shall have cooled so far' as that itmay be safely opened a sufiioient quantity of cream of lime is to beadded to the mass within the dige'ster, the said cream' of lime I burnedlime by slaking the same with excess bf hot water. After the addition ofthe lime, the digester is to be closed as before, agitation recommencedand heat again applied and continued for one or two hours or more, afterwhich the digester isto'be alhaving been recently made from freshlylowed to cool sufiiciently to permit of the contained semi-fluid massbeing transferred therefrom to a filter-bed of any suitable porousmaterial; when most of the liquid part of the mass shall have drainedoff and passed through the filtering medium, the solids on the filterare to be washed with a limited quantity of hot water, these wash waterspassing through the filter bed andincreasing the volume of the filtratewhich now contains much sodium aluminate (Na Al O From the solution ofsodium aluminate, alumina is to-be precipitated by passing through thesaid solution gaseous carbon dloxid after which the liquid which is tobe separated from the precipitated alumina by filtration, to which is tobe added the first portions of water which is to be used freely forwashing the precipitated alumina, becomes a solution of sodium carbonate(Na,CO which may be converted 'acter and constituents of the clay andare to be determinedthe quantity" of the caustic sodaby thecontainedamount of alumina v and' 'the quantity of lime by the contained amountof silica; for example, each one hundred pounds of a purekaolinitecontaining thirty-nine per cent of alumina, forty-five and ahalf per cent.

1 of silica and fifteen and a half per cent.

of water would require nineteen pounds of caustic soda (actual NaOH) andforty-two and a half pounds of lime (actual CaO); a larger quantity ofcaustic soda maybe used and a less amount of lime and the volumes ofwater are not to be determined by the quantities of soda and lime alone,but also by the physical characters of the different clays, spme ofwhich'require more water than others in order to form a bodysufficiently fluid to be agitated throughout when a portion thereof isforcibly stirred; for the quantities of soda and lime above specifiedthe caustic soda may be dissolved I in 27 gallons of water and, allowingthree lime, an additional 12 to 15 gallons will suffice to form thecream of lime.

The solution of'caustic soda may contain ten per cent. of sodiumhydroxid, but preferably it. should, usually, be a moreconcentrate'dsolution in which instance aqueous solution of the produced sodiumaluminate is facilitated by the water of the cream of lime which amountof water may and in practice Will vary within wide limits, thesedetermined by the characters of the clays.

\Vhat I claim as my invention and desire to secure by Letters Patent is:

in subjecting the natural clay to the chemical action of a solution ofcaustic alkali under heat and pressure, afterward adding to the Theherein described process of-producing. alumina from clays, which processconslsts mass cream of lime, with renewed application of heat andpressure, then separating by filtration the solution of alkali-metalaluminate so formed, then precipitating alumina from the filtrate bytreatment with carbon dioxid at the ordinary temperature,

substantially as described.

In testimony whereof I have signed this ,then washing and drying thisprecipitate,

specification in the presence of two subscrib- I ing witnesses.

EDWARD D. KENDALL. Witnesses:

FRANK E. R FMAN,

gallons of Water forthe hydration of the PAUL H. FRANK.

